Sealed inductor



M. D. BETTS SEALED INDUCTOR Dec. 28, 1965 Filed July 11, 1962 INVENTOR. 1715: Q ,fljefz?! BY Mada/ flTT'V) United States Patent 3,226,664 SEALED INDUCTOR Mazeppa D. Betts, Rockport, Mass., assignor to Sylvania Electric Products, Inc., Wilmington, Del., a corporation of Delaware Filed July 11, 1962, Ser. No. 209,059 2 Claims. (Cl. 33696) This invention relates to electromagnetic inductors such as transformers and reactors and particularly to a sealed housing for such inductors.

A typical transformer, for example, may include a ferromagnetic core shaped like a rectangular figure 8 with coil windings disposed around the middle leg of the 8. The coil extends from one side of the core through the upper opening of the 8 to the other side of the core and thence back to the first side of the core. In a simple transformer the coil may include two insulated wires, one having more turns than the other, but the coil may be considered as a unit. Where the coil extends out of the core openings beyond each side of the core the windings, though insulated, are exposed to damage. But it is customary, where the coil carries high voltage or currents, to cover it with a sheet metal housing known as an end bell. Further to protect the coil from moisture and to isolate it from the end bell and the exterior it is desirable to fill the end bell with an insulating material.

Hitherto it has been the practice to drill large holes in the end bell to admit the insulating material. Thereafter the holes must be sealed with plugs and to compensate for imperfect distribution of the insulating ma terial to confine within the end bell fumes which might be generated in the event that the transformer becomes excessively heated by reason of overloading or short circuiting in the coil. The plug also seals the interior of the end bell from atmospheric conditions.

The object of the present invention is to provide an end bell covered inductor which affords better insulation of the coil but which eliminates the use of large openings in the end bell and the plugs necessary to close such openings. Thereby the extra expense of the plugs and the manufacturing operations of inserting them in the openings can be avoided, a simpler sealing method can be employed, and an inductor with a better insulated coil is made available.

According to the invention an inductor comprises a core having windings around said core, an end bell attached to said core at one side of said core, said end bell having a cap portion extending away from the side of the core and spaced from and enclosing the coil and a web extending from said end bell along the side of the core, means holding said end bell tightly against said core so as to enclose an interior space around the coil, said web having a channel shaped portion adjacent the core and forming with the core, a passage extending from the exterior of the end bell to the interior space around said coil for conducting a solidifying sealing fluid into said space.

For the purpose of illustration a typical embodiment of the invention is shown in the accompanying drawing in which:

FIG. 1 is a side elevation of a transformer, shown partly in section;

FIG. 2 is an end elevation;

FIG. 3 is a plan View;

FIG. 4 is an end elevation shown partly in section; and

FIG. 5 is an enlarged fragment of FIG. 4.

Shown in the figures is a typical transformer comprising two rectangular O-shaped core portions 1 and 2 each having windows 3 through which a coil 4 having four terminal leads 6 are wound. Two sheet metal end bells 7 are secured by welds 8 to the core portions 1 and 2, and serve to hold the core portions together and to cover so much of the coil as is not located within the core windows. The transformer is shown upside down for the purpose of showing introduction of insulating impregnant within the end bell. Normally it will be mounted on feet 9 formed on the end bell.

The end bells comprise a cap portion 11 covering the otherwise exposed portions of the coil 4, a web portion 12 extending from the cap 11 to side flanges 14 and top and bottom flanges 13 which are welded to the core. An opening 16 in the cap permits the leads 6 to be led out of the bell. The opening 16 is barely large enough to receive the leads 6 snugly, so that only very narrow spaces between the leads and between the leads and the opening remain. The end bell encloses a space around the coil which is typically about of an inch thick.

The web 12 is held by the welds tightly against the core entirely around the cap 11 and coil, and thus seals the core, as well as a dry metal to metal seal can, with the exception of the narrow spaces around the leads and .four channel shaped portions 17.

According to the invention the channels 17 are stamped in the web 12 so as to form with the opposing core 1 and 2 a small conduit, substantially longer than it is in effective diameter, extending from the interior of the cap 11 to the exterior at the edge of the web. The channels are so located and constructed that when the transformer, inverted as shown, is immersed in a solidifying insulating and sealing fluid, the fluid will flow into the end bells through the channels and substantially fill the space between the end bells and the coil so as to completely seal the coil from the atmosphere.

Further, it is highly desirable, if not essential for safety, that the lead opening 16 and the channels 17 be sealed by the fluid.

The impregnation is carried out by preheating the transformer to the temperature of the fluid bath, approximately F. in the case of polyester such as that sold by the General Electric Company under the trademark Permafil insulation. The impregnant is heated in a scalable chamber to a viscosity at which it will flow freely through the channels in the end bells but will not seep through the metal to metal seal between the end bell Webs 12 and cores 1 and 2. At such medium viscosity the elongate channels, which have an effective internal diameter of approximately inch, act as capillaries as to the insulating fluid.

While the transformer is immersed, inverted as shown, in the fluid bath, the bath chamber is sealed and a partial vacuum is drawn in the chamber thereby evacuating substantially all the air in the air spaces within the end bells. A moderate pressure is then applied in the chamber and fluid of the bath flows through the channels into the end bells.

As shown at the left of FIG. 5 the subsequently solidified insulating compound 18 may completely fill the space within the end bell and extend through capillary spaces between the leads 6 and the lead opening 16. In some cases, as shown at the right of FIG. 5 the compound 18 may coat the coil 4 but leave an air space next to the end bell cap 11. In such cases the channels 17 may still be sealed owing to the retention of a meniscus of insulating fluid as shown at 18a. Thus the interior of the end bell is completely sealed in in either case. By virtue of its being a capillary for medium viscosity fluids, other insulating compounds such as asphaltic compounds, natural or silicone resins may be used. Such compounds will also form a meniscus in the channel and seal it both to prevent the escape of fumes from within and the entry of atmospheric vapor.

Because the channels may be located in the impregnant bath above the end bell good control of filling is provided. The use of extra parts, such as plugs, is, however, eliminated as a result of the self sealing character of the channels. The channels may be any shape, semicircular as shown, triangular or rectangular, without adding any substantial cost or extra tool operation as in the case of plugged openings. Thus it should be understood that the present invention includes all modifications and equivalents falling within the appended claims.

I claim:

1. A mechanically complete inductor comprising a core, a coil having windings around said core, end bells attached to said core at two sides of said core respectively, each said end bell having a cap portion extending away from the side of the core and spaced from and enclosing the coil and a web extending from each said end bell along the side of the core, means holding each said end bell tightly against said core so as to enclose an interior space around the coil, each said web having a channel shaped portion adjacent the core and forming with the core a passage extending from the exterior of the end bell to the interior space around said coil, said passage being closed on all sides by said core and said web channel and extending along the core a greater distance than the efiective diameter of the passage, said passage forming a capillary for a sealing fluid of medium viscosity, and an integral, solidified mass of sealing compound in the space between said coil and cap forming a closure in the passage formed by said channel and core.

2. An inductor according to claim 1 wherein said passage is approximately inch to inch in efiective diameter.

References Cited by the Examiner UNITED STATES PATENTS 1,974,588 9/1934 Snell 336-96 2,732,421 1/1956 Chapman 174-76 2,741,528 4/1956 Clark et al 336--98 OTHER REFERENCES Control Transformers, Westinghouse Descriptive Bulletin 45-150, published by Westinghouse Electric Corp., Speciality Transformer Dept, Green ille Plant, Greenville, Pa., page 10.

ROBERT K. SCI-IAEFER, Primary Examiner.

JOHN P. WILDMAN, JOHN F. BURNS, LARAMIE E.

ASKIN, Examiners.

WILLIAM F. ZAGURSKI, SPENCER H. BOYER, As-

sistant Examiners. 

1. A MECHANICALLY COMPLETE INDUCTOR COMPRISING A CORE, A COIL HAVING WINDINGS AROUND SAID CORE, END BELLS ATTACHED TO SAID CORE AT TWO SIDES OF SAID CORE RESPECTIVELY, EACH SAID END BELL HAVING A CAP PORTION EXTENDING AWAY FROM THE SIDE OF THE CORE AND SPACED FROM AND ENCLOSING THE COIL AND A WEB EXTENDING FROM EACH SAID END BELL ALONG THE SIDE OF THE CORE, MEANS HOLDING EACH SAID END BELL TIGHTLY AGAINST SAID CORE SO AS TO ENCLOSE AN INTERIOR SPACE AROUND THE COIL, EACH SAID WEB HAVING A CHANNEL SHAPED PORTION ADJACENT THE CORE AND FORMING WITH THE CORE A PASSAGE EXTENDING FROM THE EXTERIOR OF THE END BELL TO THE INTERIOR SPACE AROUND SAID COIL, SAID PASSAGE BEING CLOSED ON ALL SIDES BY SAID CORE AND SAID WEB CHANNEL AND EXTENDING ALONG THE CORE A GREATER DISTANCE THAN THE EFFECTIVE DIAMETER OF THE PASSAAGE, SAID PASSAGE FORMING A CAPILLARY FOR A SEALING FLUID OF MEDIUM VISCOSITY, AND AN INTEGRAL, SOLIDIFIED MASS OF SEALING COMPOUND IN THE SPACE BETWEEN SAID COIL AND CAP FORMING A CLOSURE IN THE PASSAGE FORMED BY SAID CHANNEL AND CORE. 